So, JB asked me for further explanation on how I run Rifts with my sanity intact.
1. At the core, you're playing heavily house-ruled AD&D. You have classes, experience points, alignment, levels, hit points, saving throws, attack rolls resolved with a d20, etc. When the rules seem to get all sideways on you, just take it back to D&D.
2. House rules I use: 1 Mega-Damage=10 SDC. Pass-through damage from Rifter #30. If you don't have Rifter 30, just swap this out instead: For every 10 MD your armor takes, you suffer 1d6 SDC. Double it for impact weapons like missiles/rail guns. Half it if you're wearing heavy armor. Close enough.
3. This is meant to be a ball-out, over-the-top game. The Coalition are like the bad guys from an 80's toy line. Juicers are guys who have FUTURE STEROIDS pumped into their bodies and wear mohawks because...metal. Play this game like you're playing a heavy metal album cover from before the 90's.
4. Bring your descriptive and adjudicative A game when running combat. For Pete's sake, the characters are carrying firepower enough to level buildings. Reward them for doing bat-shit insane things.
5. When the rules make something silly happen, make a ruling. Change a number. Do whatever you need to do.
6. Don't feel obligated to include all the books, or even most of them, in a given campaign. My Rifts game takes place in and around Madhaven, which is the ruins of New York City. There's no stuff from Rifts Russia or Rifts Australia or Skraypers or anything like that. The books KS releases detail the entire world. There's more than enough material in the core book and one or two splats to fuel a campaign.
I'm not sure if this is what you were looking for, but they are a few more specific points that I use to keep the game in perspective. The first rule overrides all the other rules. You are playing something akin to Arduin, but with cyborgs. (Did Arduin have cyborgs in it? I confess I am ignorant when it comes to all things Hargrave.)